Re: var->index versus var in linreg code

[Jason Stover]

I can't think of any problems this would cause.

On Tue, Dec 05, 2006 at 08:01:58PM -0800, Ben Pfaff wrote:
> Hi Jason.  While looking over code, I noticed a number of
> comparisons in linreg.c, coefficient.c, and design-matrix.c of
> the form "var1->index == var2->index".  I think that in each case
> this could be replaced by "var1 == var2".
> 
> With your permission, I'd like to check in the following change
> that takes advantage of this.  It still passes "make check", so
> unless you're aware of some kind of subtlety, I think it is
> correct:
> 
> Index: src/math/coefficient.c
> ===================================================================
> RCS file: /cvsroot/pspp/pspp/src/math/coefficient.c,v
> retrieving revision 1.5
> diff -u -p -r1.5 coefficient.c
> --- src/math/coefficient.c    5 Dec 2006 15:10:21 -0000       1.5
> +++ src/math/coefficient.c    6 Dec 2006 03:59:26 -0000
> @@ -169,7 +169,7 @@ pspp_coeff_get_value (struct pspp_coeff 
>    while (i < c->n_vars)
>      {
>        candidate = pspp_coeff_get_var (c, i);
> -      if (v->index == candidate->index)
> +      if (v == candidate)
>       {
>         return (c->v_info + i)->val;
>       }
> @@ -201,7 +201,7 @@ pspp_linreg_get_coeff (const pspp_linreg
>  
>    result = c->coeff[i];
>    tmp = pspp_coeff_get_var (result, 0);
> -  while (tmp->index != v->index && i < c->n_coeffs)
> +  while (tmp != v && i < c->n_coeffs)
>      {
>        result = c->coeff[i];
>        tmp = pspp_coeff_get_var (result, 0);
> @@ -221,7 +221,7 @@ pspp_linreg_get_coeff (const pspp_linreg
>           If v is categorical, we need to ensure the coefficient
>           matches the VAL.
>         */
> -      while (tmp->index != v->index && i < c->n_coeffs
> +      while (tmp != v && i < c->n_coeffs
>            && compare_values (pspp_coeff_get_value (result, tmp),
>                               val, var_get_width (v)))
>       {                       /* FIX THIS */
> Index: src/math/design-matrix.c
> ===================================================================
> RCS file: /cvsroot/pspp/pspp/src/math/design-matrix.c,v
> retrieving revision 1.4
> diff -u -p -r1.4 design-matrix.c
> --- src/math/design-matrix.c  5 Dec 2006 15:10:21 -0000       1.4
> +++ src/math/design-matrix.c  6 Dec 2006 03:59:26 -0000
> @@ -146,8 +146,8 @@ design_matrix_destroy (struct design_mat
>    Return the index of the variable for the
>    given column.
>   */
> -static size_t
> -design_matrix_col_to_var_index (const struct design_matrix *dm, size_t col)
> +struct variable *
> +design_matrix_col_to_var (const struct design_matrix *dm, size_t col)
>  {
>    size_t i;
>    struct design_matrix_var v;
> @@ -156,42 +156,11 @@ design_matrix_col_to_var_index (const st
>      {
>        v = dm->vars[i];
>        if (v.first_column <= col && col <= v.last_column)
> -     return (v.v)->index;
> -    }
> -  return DM_INDEX_NOT_FOUND;
> -}
> -
> -/*
> -  Return a pointer to the variable whose values
> -  are stored in column col.
> - */
> -struct variable *
> -design_matrix_col_to_var (const struct design_matrix *dm, size_t col)
> -{
> -  size_t index;
> -  size_t i;
> -  struct design_matrix_var dmv;
> -
> -  index = design_matrix_col_to_var_index (dm, col);
> -  for (i = 0; i < dm->n_vars; i++)
> -    {
> -      dmv = dm->vars[i];
> -      if ((dmv.v)->index == index)
> -     {
> -       return (struct variable *) dmv.v;
> -     }
> +     return (struct variable *) v.v;
>      }
>    return NULL;
>  }
>  
> -static size_t
> -cmp_dm_var_index (const struct design_matrix_var *dmv, size_t index)
> -{
> -  if (dmv->v->index == index)
> -    return 1;
> -  return 0;
> -}
> -
>  /*
>    Return the number of the first column which holds the
>    values for variable v.
> @@ -206,7 +175,7 @@ design_matrix_var_to_column (const struc
>    for (i = 0; i < dm->n_vars; i++)
>      {
>        tmp = dm->vars[i];
> -      if (cmp_dm_var_index (&tmp, v->index))
> +      if (tmp.v == v)
>       {
>         return tmp.first_column;
>       }
> @@ -225,7 +194,7 @@ dm_var_to_last_column (const struct desi
>    for (i = 0; i < dm->n_vars; i++)
>      {
>        tmp = dm->vars[i];
> -      if (cmp_dm_var_index (&tmp, v->index))
> +      if (tmp.v == v)
>       {
>         return tmp.last_column;
>       }
> Index: src/math/linreg/linreg.c
> ===================================================================
> RCS file: /cvsroot/pspp/pspp/src/math/linreg/linreg.c,v
> retrieving revision 1.15
> diff -u -p -r1.15 linreg.c
> --- src/math/linreg/linreg.c  19 May 2006 21:08:20 -0000      1.15
> +++ src/math/linreg/linreg.c  6 Dec 2006 03:59:27 -0000
> @@ -123,7 +123,7 @@ pspp_linreg_get_vars (const void *c_, st
>        /* Repeated variables are likely to bunch together, at the end
>           of the array. */
>        i = result - 1;
> -      while (i >= 0 && (v[i]->index != tmp->index))
> +      while (i >= 0 && v[i] != tmp)
>       {
>         i--;
>       }
> 
> 
> -- 
> "I ran it on my DeathStation 9000 and demons flew out of my nose." --Kaz
> 
> 
> 
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-- 
Jason H. Stover
Assistant Professor
Mathematics Department
Georgia College & State University